Antitumor drugs alter the cell cycle distribution and topo IIα and IIβ contents of HL-60 cells. DNA histograms (A through D), two-dimensional flow cytometric analyses of DNA-topo IIα contents (E through H), DNA-topo IIβ contents (I through L), and DNA content-TUNEL assay (M through P) of control and Ara-C–, etoposide-, and vincristine-treated HL-60 cells.